Improving indoor air quality and thermal comfort using a total heat exchanger ventilation system for an office building

Abstract

Indoor air quality (IAQ) and thermal comfort affect occupant comfort and productivity. Thermal comfort supports productivity, while IAQ maintains occupant health. However, occupants are the main source of carbon dioxide, which is the main index for indoor pollutants in educational buildings due to many occupants gathering in one room. This study investigates the performance of applying a total heat exchanger (THX) for diluting carbon dioxide (CO2). Besides, the thermal comfort of the occupants has been evaluated extensively as the THX also reduces the fresh air temperature. An office area with 14 graduate students seated in a meeting was investigated. Questionnaires and field measurements were conducted simultaneously. Time-varying IAQ (carbon dioxide concentration) was assessed using computational fluid dynamics. The numerical simulation program also contained User Defined Function (UDF) based predicted mean vote (PMV) algorithms to determine occupant thermal comfort. The results indicated that without using THX, the CO2 concentration gradually rises until it reaches a maximum of 1400 ppm inside the room. This condition occurs because there is no air change between indoor and fresh air, mainly due to the lack of fresh air supply and reliance on split AC for circulation. With THX, the concentration could lower to below 1000 ppm. In addition, it also could make room temperature slightly lower, with the overall temperature average in this study being 24.5?C without THX and 24.1?C when THX is operated.